Engine Exhaust Heat

[bgsengine]

Pressure was checked at the O2 sensor and their was no back pressure to speak of.

There actually SHOULD BE a slight backpressure.

I believe OEM exhaust has two seperate tubes off the heads to a muffler.

There are various configurations, but essentially yes. They can also have 2 tubes coming out to a collector.. BUT..

This manifold has the two come together into a collector and then down stream in an 1.5" pipe. Them failure comes after the collector.

Therein lies the problem - You cannot have a solid 1-piece manifold and collector assembly together - the cylinders and therefore the mountings will have a different rate of expansion and contraction because they are not cooled evenly (One runs slightly hotter than the other) SOOOO .. you would need 2 separate pipes that *can* come together to a collector, BUT they should be connected as a "slip fit" and clamped to allow for differences in expansion rates - If it is all solid one piece welded assembly, that'll cause you uneven stresses and cracking failures in any case, with or without the red hot exhaust.

Also, MOST ALL exhaust pipes will glow red hot , if you have them in a darkened room, or enclosed space you're talking about temperatures approaching 1500 degrees so of course most any metal is gonna have some heat signature showing in the dark. I would be focusing on the problem of using stainless steel material in the exhaust and also check and see if the pipes are assembled and clamped (slip fitted) or if the manifold and collector is all one welded assembly - if it is all one piece, that is one big part of the problem as far as failure goes.. whether or not Kohler approved the exhaust, if there's no room for the pipes to slip instead of flex, then eventually you're gonna have metal fatigue failures. (Even the OEM mufflers do that eventually when they ate bolted direct to the heads, rather than clamped to "stubs" (allowing for the aforementioned "slip fit") , but as the muffler can has more "give" to it, it can take a lot more than a welded stainless steel pipe.)

So, as the engine operation and outputs appear to be within normal operating parameters, I would not be looking at the engine as being the cause of any failures. Now, if you got pipes that glow red hot in broad daylight / direct light, then I'd be thinking the engine is a tad lean AND the exhaust pipes are a bit thin..